Plasma display device and method of manufacturing same

ABSTRACT

A plasma display device including a green phosphor of which brightness is hardly deteriorated and a production method therefor are disclosed. The plasma display device comprises a plasma display panel in which a plurality of discharge cells of one color or a plurality of colors are disposed, red phosphor layers  110 R, green phosphor layers  110 G, and blue phosphor layers  110 B are arranged correspondingly to the respective discharge cells, and the red phosphor layers  110 R, the green phosphor layers  110 G, and the blue phosphor layers  110 B are excited by ultraviolet rays to emit light. The green phosphor layers  110 G include a green phosphor expressed by (M a-x-y Eu x Tb y )O.MgO.2SiO 2  (here, M is at least one element selected from Ca, Sr, and Ba).

TECHNICAL FIELD

The present invention relates to a plasma display device which can beused for image display of a television or the like and a method ofmanufacturing the same.

BACKGROUND ART

In recent years, in a color display device which is used for imagedisplay of a computer, a television, or the like, a plasma displaydevice which uses a plasma display panel (hereinafter, refers to as a‘PDP’ or a ‘panel’) has received attention as a color display panelwhich can realize a thin thickness and a lightness with a large size.

The plasma display device performs full color display by performing anadditive color mixture of so-called three primary colors (red, green,blue). In order to perform such a full color display, the plasma displaydevice includes phosphor layers which emit light components of the threeprimary colors, which are red (R), green (G), and blue (B). A phosphorparticle constituting the phosphor layer is excited by ultraviolet raysgenerated inside discharge cells of the PDP to emit visible light ofeach color.

As chemical compounds used as color phosphors, for example, (Y,Gd)BO₃:Eu, Y₂O₃:Eu which emits a red light component, Zn₂SiO₄:Mn whichemits a green light component, BaMgAl₁₀O₁₇:Eu which emits a blue lightcomponent are known. As a method of manufacturing each of the phosphors,an example in which predetermined raw materials are mixed with eachother and then solid-phase reaction is performed by baking the mixtureat a temperature of 1000° C. or more is disclosed at ‘phosphor handbook’(P 219, 225, published by Ohmsha, Ltd.). Further, the phosphor particleobtained by the baking process is apt to be sintered by the bakingprocess. Therefore, the phosphor particle is used after being grindedand sorted (a mean particle size of red and green phosphor is 2 μm to 5μm, a mean particle size of blue phosphor is 3 μm to 10 μm).

However, since a phosphor particle of the conventional Zn₂SiO₄: Mn whichemits a green light component is manufactured through a grinding processafter solid-phase reaction, stress is applied to a surface of thephosphor particle to occur strain, and various defects such as so-calledoxygen defect are generated. Therefore, there is a problem in that sucha defect absorbs water contained in the atmosphere during the process ofmanufacturing the panel, water reacts with the phosphor inside the panelduring the time of raising the temperature when the panel is sealed up,such that the brightness of the phosphor deteriorates. Further, thedefect absorbs ultraviolet rays of 147 nm which is generated due to thedischarge, such that the excitation of the light-emitting center isinterrupted. Furthermore, there is another problem in that water reactswith MgO serving as a protecting film inside the panel to cause anaddress discharge miss. Further, the phosphor of Zn₂SiO₄:Mn is easilysuffered from ion impaction. As a result, there is still another problemin that the deterioration of the brightness is significant, such thatsufficiently high brightness can not be obtained. Furthermore, since theZn₂SiO₄:Mn is negatively-charged, the charging tendency thereof isdifferent from that of the red phosphor or the blue phosphor. Therefore,there is problem in that the discharge error may be easily generated.

DISCLOSURE OF THE INVENTION

The plasma display device according to the present invention is a plasmadisplay device in which a plurality of discharge cells of one color or amultiple colors are disposed, a plurality of phosphor layerscorresponding to colors of the respective discharge cells are disposed,and the phosphor layers are excited by ultraviolet rays to emit light.The phosphor layers include green phosphor layers, and the greenphosphor layers include a green phosphor expressed by(M_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (here, M is at least one elementselected from Ca, Sr, and Ba).

According to the present invention, it is possible to provide a plasmadisplay device including a green phosphor in which the deterioration ofthe brightness is hardly generated during the time of manufacturing thepanel and to improve the brightness, the durability, the reliability ofthe plasma display device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a PDP used in a plasma display device accordingto an embodiment of the present invention, in which a front glasssubstrate is not shown.

FIG. 2 is a perspective view showing a structure of an image displayregion of the PDP used in the plasma display device according to theembodiment of the present invention.

FIG. 3 is a block diagram of the plasma display device according to theembodiment of the present invention.

FIG. 4 is a sectional view showing a structure of the image displayregion of the PDP used in the plasma display device according to theembodiment of the present invention.

FIG. 5 is a schematic configuration view showing an ink applying devicewhich is used for forming phosphor layers of PDP used in the plasmadisplay device according to the embodiment of the present invention.

REFERENCE NUMERALS

100: PLASMA DISPLAY PANEL (PDP)

101: FRONT GLASS SUBSTRATE

103: DISPLAY ELECTRODE

104: DISPLAY SCAN ELECTRODE

105, 108: DIELECTRIC GLASS LAYER

106: PROTECTIVE LAYER

107: ADDRESS ELECTRODE

109: BARRIER RIB

110R: RED PHOSPHOR LAYER

110G: GREEN PHOSPHOR LAYER

110B: BLUE PHOSPHOR LAYER

122: DISCHARGE SPACE

150: PDP DRIVING DEVICE

160: PLASMA DISPLAY DEVICE

BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, the phosphor expressed by(M_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂(here, M is at least one elementselected from Ca, Sr, and Ba) is manufactured by any one of an aqueoussolution synthesis method, a spray synthesis method, a hydrothermalsynthesis method, and a hydrolysis synthesis method which can easilyobtain a particle having a substantially spherical shape. Specifically,a precursor of the phosphor is manufactured from a raw material of thephosphor. Since the precursor of the phosphor has a substantiallyspherical shape, even though the precursor is thermally-treated at ahigh temperature of 1000° C. to 1400° C., each particle hardly bonds toeach other, such that the phosphor in which its substantially sphericalshape is maintained is obtained. Further, the term ‘substantiallyspherical shape’ means that an axis diameter ratio (short axisdiameter/long axis diameter) of almost phosphor particles is maintained,for example, within a range of 0.9 to 1.0 and it is not necessary thatwhole phosphor particles are maintained within the range.

Therefore, the phosphor is grinded only a little, such that the phosphorwhose brightness is high and whose amount of defect is small can beobtained. Further, since ZnO is not contained in the composition of thephosphor like the conventional Zn₂SiO₄:Mn, even though the phosphor isbaked at a high temperature of 1000° C. to 1400° C., a specific rawmaterial does not selectively sublimate, and the deviation incomposition of the phospher does not occur. Therefore, it is possible toobtain the green phosphor with the excellent durability characteristic.

Further, since the phosphor formed by the manufacturing method accordingto the present invention is small in diameter, is uniform in particlesize distribution, and is excellent in crystalline property, the fillingdensity of the phosphor particle is improved when the phosphor layer isformed. Therefore, a light-emitting area of the phosphor particle whichsubstantially takes part in light emission is increased, and thephosphor does not readily deteriorate due to the discharge. Thus, eventhough the discharge space is small in, for example, a PDP whichdisplays a high definition image, it is possible to obtain a highbrightness.

Hereinafter, four kinds of methods as a specific method of manufacturingthe phosphor will be described by taking a green phosphor as an example.

First, the aqueous solution synthesis method will be described. As rawmaterials of a phosphor, barium nitrate Ba(NO₃)₂, calcium nitrateCa(NO₃)₂, strontium nitrate Sr(NO₃)₂, magnesium nitrate Mg(NO₃)₂,silicon oxide SiO₂ (colloidal silica), ethyl silicate Si(O.C₂H₅)₄,europium nitrate Eu(NO₃)₃, and terbium nitrate Tb(NO₃)₃ are used. Thisraw material of the phosphor is dissolved in an aqueous medium to thusprepare an aqueous mixture (a step of preparing a mixture). Then, themixture is bubbled by using oxygen (O₂), ozone (O₃), or oxygen-nitrogen(O₂—N₂) while applying ultrasonic waves thereto, and an alkaline aqueoussolution is added to and mixed with the mixture to thus prepare ahydrate which is a precursor of phosphor (a step of preparing ahydrate). And then, a solution containing the precursor of the phosphorobtained from the step of preparing the hydrate is heat-treated in theair at a temperature of 700° C. to 900° C. to thus obtain a precursorpowder of the phosphor (a step of a heat treatment). And then, theprecursor powder of the phosphor is baked at a temperature of 1000° C.to 1400° C. under a reducing atmosphere (a step of baking) to thusmanufacture a green phosphor which is substantially spherical shapedpowder.

Next, the spray synthesis method will be described. The step ofpreparing the mixture and the step of preparing the hydrate, which aredescribed in the aqueous solution synthesis method, are performed. Then,liquid droplets of the alkaline aqueous solution containing theprecursor of the phosphor obtained from the step of preparing thehydrate are sprayed into a furnace heated at a temperature of 1000° C.to 1500° C. (a step of spraying) to thus prepare a precursor powder ofthe phosphor. And then, the precursor powder of the phosphor is baked ata temperature of 1000° C. to 1400° C. under a reducing atmosphere tothus manufacture a green phosphor which is substantially sphericalshaped powder.

Next, the hydrothermal synthesis method will be described. The step ofpreparing the mixture and the step of forming the hydrate, which aredescribed in the aqueous solution synthesis method, are performed. Then,the alkaline aqueous solution containing the precursor of the phosphorobtained from the step of forming the hydrate is put into a highlypressured container and is applied with a pressure of 0.2 MPa to 10 MPaat a temperature of 100° C. to 300° C. to perform a hydrothermalsynthesis reaction (a step of a hydrothermal synthesis), therebyobtaining a precursor powder of the phosphor. And then, the precursorpowder of the phosphor is baked at a temperature of 1000° C. to 1400° C.under a reducing atmosphere to thus manufacture a green phosphor whichis substantially spherical shaped powder.

Next, the hydrolysis synthesis method will be described. An organiccompound containing each of Ca, Sr, Ba, Mg, Si, Eu, and Tb (metal acetylacetone and metal alkoxide) is used as a raw material of the phosphor.The raw material of the phosphor, alcohol, and water are mixed and theresultant mixture is hydrolysis-reacted to thus manufacture a precursorof the phosphor. Then, the precursor of the phosphor is heat-treated ata temperature of 700° C. to 900° C. to thus obtain a precursor powder ofthe phosphor. And then, the precursor powder of the phosphor is baked ata temperature of 1000° C. to 1400° C. under a reducing atmosphere tothus manufacture a green phosphor which is substantially sphericalshaped powder.

In the aqueous solution synthesis method, the spray synthesis method,the hydrothermal synthesis method, and the hydrolysis synthesis methoddescribed above, the precursor of the phosphor has a substantiallyspherical shape. Therefore, the green phosphor particle obtained fromthe precursor has also the substantially spherical shape, and has asmall particle size of 0.05 μm to 3 μm, and is excellent in a particlesize distribution. As a result, the filling density of the phosphorparticle is improved when the phosphor layer is formed. Therefore, alight-emitting area of the phosphor particle which substantially takespart in light emission is increased. Thus, even though the dischargespace volume of a PDP is one third of that of the conventional PDP andthe film thickness of the phosphor is one third of that of theconventional PDP, the brightness of the plasma display device isimproved and the deterioration of the brightness is suppressed, suchthat it is possible to obtain a plasma display device excellent in thebrightness characteristics.

Specifically, instead of the green phosphor of Zn₂SiO₄:Mn in which thedeterioration of the brightness is large, a green phosphor expressed byfollowing chemical formula, (M_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (here, Mis at least one element selected from Ca, Sr, and Ba) is used, such thatvarious deterioration can be largely improved.

Here, it is preferable that the mean particle size of the green phosphoris 0.1 μm to 3 μm. Further, it is preferable that in the particledistribution, the maximum particle size is 8 μm or less, and the minimumparticle size is one fourth or more of the mean particle size. In thephosphor particle, a region to which ultraviolet rays reach is thin, forexample, several hundreds nm from the particle surface, such thatsubstantially only the particle surface emits a light. Therefore, whenthe mean particle size of the phosphor is 3 μm or less, the surface areaof particle which participates in the light emission increases and thelight emission efficiency is maintained at a high state. Further, whenthe mean particle size of the phosphor exceeds 3 μm, the thickness ofthe phosphor layer needs to be 20 μm or more, so that the dischargespace is not sufficiently secured. On the other hand, when the meanparticle size of the phosphor is less than 0.1 μm, the defect is easilygenerated and the brightness is not improved.

Hereinafter, a plasma display device according to an embodiment of thepresent invention will be described with reference to the attacheddrawings.

FIG. 1 is a plan view of PDP 100, in which front glass substrate 101 isremoved. FIG. 2 is a perspective view showing a part of image displayregion 123 of PDP 100 shown in FIG. 1. Further, in FIG. 1, the number ofdisplay electrodes 103, display scan electrodes 104, address electrodes107, or the like is partially omitted for the purpose of easyunderstanding. The structure of PDP 100 is described with reference toFIGS. 1 and 2.

As shown in FIG. 1, PDP 100 includes front glass substrate 101 (notshown), rear glass substrate 102, N display electrodes 103, N displayscan electrodes 104 (in the case of indicating n-th electrode, thenumber n is written inside parentheses), M address electrodes 107 (inthe case of indicating m-th electrode, the number m is written insideparentheses), air-tight sealing layer 121 shown by oblique lines, or thelike. Electrode matrix of three-electrode structure by electrodes 103,104, and 107 is formed and discharge cells are formed at intersectionsof display electrodes 103 and display scan electrode 104, and addresselectrodes 107.

As shown in FIG. 2, PDP 100 is formed by laminating a front panel inwhich display electrodes 103, display scan electrodes 104, dielectricglass layer 105 and protective layer 106 are disposed at one mainsurface of front glass substrate 101, and a rear panel in which addresselectrodes 107, dielectric glass layer 108, barrier ribs 109, redphosphor layers 110R, green phosphor layers 110G and blue phosphorlayers 110B are disposed at one main surface of rear glass substrate102. Discharge gas composed of for example, neon (Ne), xenon (Xe), orthe like is filled into the inside of discharge spaces 122 formedbetween the front panel and the rear panel.

FIG. 3 is a block diagram of the plasma display device according to theembodiment of the present invention. Plasma display device 160 shown inFIG. 3 is constructed by connecting PDP driving device 150 to PDP 100.PDP driving device 150 is constructed by display driver circuit 153 fordriving display electrodes 103, display scan driver circuit 154 fordriving display scan electrodes 104, address driver circuit 155 fordriving address electrodes 107, and controller 152 for controllingabove-described circuits. At the time of driving plasma display device160, according to the control of controller 152, a pulse voltage isapplied to display scan electrodes 104 and address electrodes 107 of thedischarge cells to be turned on, and an address discharge is performedtherebetween. Then, the pulse voltage is applied between displayelectrodes 103 and display scan electrodes 104, and a sustain dischargeis performed. Ultraviolet rays are generated at the discharge cells bythe sustain discharge, and the phosphor layer, which is excited by theultraviolet rays, emits light, such that the discharge cells are turnedon. By doing so,images are displayed by association of turn on and offof the discharge cells in which phosphor layers of each color areformed.

Hereinafter, a method of manufacturing PDP 100 described above will bedescribed with reference to FIGS. 1 and 2.

The front panel is manufactured such that on front glass substrate 101,N display electrodes 103 and display scan electrodes 104 (in FIG. 2,only two display electrodes and two display scan electrodes are shown)are alternately formed in strips and in parallel to each other,dielectric glass layer 105 is formed so as to cover display electrodes103 and display scan electrodes 104, and then protective layer 106 isformed on the surface of dielectric glass layer 105.

Display electrodes 103 and display scan electrodes 104 are electrodescomprised of a transparent electrode made of ITO(indium tin oxide) and abus electrode made of a metal material such as silver. For example, anITO film is formed at almost entire surface on front glass substrate 101by a sputter method, transparent electrodes having a predeterminedpattern (in strips) are formed by patterning the ITO film by etchingmethod, silver paste for bus electrode is applied to the transparentelectrodes by a screen printing, and the silver pastes are baked to thusform the display electrodes 103 and display scan electrodes 104.

Dielectric glass layer 105 having a predetermined layer-thickness (about20 μm) is formed by applying a paste including lead-based glass materialby a screen printing method, and by baking at a predeterminedtemperature and for a predetermined time (for example, at 560° C., fortwenty minutes). For example, a mixture of an organic binder, and PbO(70 wt %), B₂O₃ (15 wt %), SiO₂ (10 wt %) and Al₂O₃ (5 wt %) is used asthe paste including the lead-based glass material. Here, the organicbinder is formed by dissolving a resin in an organic solvent. Forexample, the organic binder is formed by dissolving 10% ethyl cellulosein α-terpineol. In addition to the ethyl cellulose, it is possible touse an acryl resin as the resin and butylcarbitol as the organicsolvent. Further, for example, glyceryltrioleate or the like may beadded to the organic binder as a dispersant.

Protective film 106 is composed of magnesium oxide (MgO) and is formedto have a predetermined thickness (about 0.5 μm), for example, by asputtering method, a CVD method (chemical vapor deposition method).

The rear panel is formed by following process. First, a silver paste forelectrode is screen-printed on rear glass substrate 102 and baked tothus form M address electrodes 107. A paste containing lead-based glassmaterial is applied to cover address electrodes 107 using a screenprinting method to thus form dielectric glass layer 108. The same pastecontaining lead-based glass material is repeatedly applied with apredetermined pitch by the screen printing method and is baked to thusform barrier ribs 109. Due to barrier ribs 109, discharge space 122 aredivided into each discharge cell (unit light-emission region) in adirection parallel to discharge electrodes 103 and display scanelectrodes 104.

FIG. 4 is a partial sectional view of PDP 100. As shown in FIG. 4, gapwidth (W) between barrier ribs 109 is defined by about 130 μm to 240 μmin accordance with HD-TV of 32 inches to 50 inches. Then, a paste-shapedphosphor ink composed of a phosphor particle of red (R), green (G), andblue (B), and an organic binder is applied between barrier ribs 109. Andthen, rear glass substrate to which the paste-shaped phosphor ink isapplied is burned at a temperature of 400° C. to 590° C. to burn awaythe organic binder, thereby forming red phosphor layers 110R, greenphosphor layers 110G, and blue phosphor layers 110B, which are composedof each phosphor particle.

It is preferable that the thickness (L) in a laminating direction of redphosphor layers 110R, green phosphor layers 110G, and blue phosphorlayers 110B on address electrodes 107 is 8 times to 25 times of the meanparticle size of each color phosphor particle. Specifically, to securethe brightness (light emission efficiency) when regular ultraviolet raysare irradiated to the phosphor layer, it is preferable that thethickness of the phosphor is determined to secure a predeterminedthickness in which the phosphor particles are laminated as at least 8layers, and preferably 20 layers, so that ultraviolet rays generated inthe discharge spaces is not transmitted therethrough. On the other hand,when the phosphor particles are made to have a thickness in which thephosphor particles are laminated as 25 layers or more, the lightemission efficiency of the phosphor layer is saturated and the size ofdischarge space 122 can not be sufficiently secured.

Further, if the phosphor particle is sufficiently small in the particlesize and has a substantially spherical shape, like that manufactured bythe precursor of the phospher by use of the aqueous solution synthesismethod, the hydrothermal synthesis method, the spray synthesis method,and the hydrolysis synthesis method, even though the number oflaminating stage is equal, the filling density of the phosphor particleis increased as compared with particles not in a substantially sphericalshape. As a result, since the total surface area of the phosphorparticle increases, the surface area of the phosphor particleparticipating in actual light emission in the phosphor layer increases,whereby the light emission efficiency increases.

The front panel and rear panels manufactured by the above process arebonded together in a process of sealing the panels such that displayelectrodes 103 and display scan electrodes 104 of the front panel andaddress electrodes 107 of the rear panel are perpendicular to eachother. At this time, a sealing glass is interposed between theperipheries of the panels and baked at a temperature about 450° C. for10 minutes to 20 minutes to form air-tight seal layer 121 (FIG. 1),thereby sealing the panels. Then, first, air inside of discharge spaces122 are exhausted at a highly vacuumed chamber (for example, 1.1×10⁻⁴Pa), discharge gas (for example, Ne—Xe based, He—Xe based inert gas) isfilled thereto to thus manufacture PDP 100.

FIG. 5 is a schematic configuration view of an ink applying device whichis used when red phosphor layers 110R, green phosphor layers 110G, andblue phosphor layers 110B are formed.

As shown in FIG. 5, ink applying device 200 includes server 210,pressing pump 220, and header 230. The phosphor ink supplied from server210 containing phosphor ink is pressured by pressuring pump 220 andsupplied to header 230. Header 230 includes ink chamber 230 a and nozzle240. The phosphor ink which is supplied to pressured ink chamber 230 ais continuously ejected through nozzle 240. It is preferable that adiameter D of nozzle 240 is 30 μm or more for preventing the nozzle frombeing plugged and is less than the distance W (about 130 μm to 240 μm)between barrier ribs 109 for preventing the ink from running over thebarrier ribs during the time of applying ink. Generally, the diameter Dis set within a range of 30 μm to 130 μm.

Header 230 is constructed such that it is linearly driven by a scanningmechanism (not shown). The phosphor ink 250 is continuously ejected fromnozzle 240 while header 230 is scanned, such that the ink is uniformlyapplied to grooves between barrier ribs 109 on rear glass substrates102. Here, the viscosity of the used phosphor ink is maintained in arange of 1500 CP to 30000 CP (centipoise) at a temperature of 25° C.

Further, server 210 includes an agitating device (not shown), and aprecipitation of the phosphor particle in the phosphor ink is preventeddue to the agitating operation thereof. Furthermore, header 230 isintegrated with ink chamber 230 a and a part of nozzle 240, and ismanufactured by a mechanical process of metal materials and a dischargeprocess.

Further, as a method of forming the phosphor layer, it is not limited tothe above-described method, various methods such as photolithographymethod, a screen printing method, and a method of disposing a film whichis mixed with the phosphor particle can be used.

The phosphor ink is manufactured by mixing a phosphor particle of eachcolor, a binder, and a solvent to have a viscosity of 1,500 CP to 30,000CP. Further, as desired, a surfactant, silica, a dispersant (0.1 wt % to5 wt %) may be added to the resultant mixture.

As a red phosphor mixed to the phosphor ink, compound expressed by (Y,Gd)_(1-x)BO₃:Eu_(x) or (Y_(1-x))₂O₃:Eu_(x) is used.

As a blue phosphor, a compound expressed by Ba_(1-x)MgAl₁₀O₁₇: Eu_(x) orBa_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x) is used.

As a green phosphor, a compound expressed by(M_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (here, M is at least one elementselected from Ca, Sr, and Ba) is used, and a part of element M (Ca, Sr,Ba) constituting a parent material is substituted with Eu, Tb to obtaina green light emission.

As a binder mixed to a phosphor ink, ethyl cellulose or acryl resin(mixed as a ratio of 0.1 wt % to 10 wt % of the phosphor ink) is used,and α-terpineol or butyl carbitol is used as a solvent. Further, apolymer such as PMA (methyl polyacrylate), PVA (polyvinyl alcohol) maybeused as the binder, and an organic solvent such as diethylene glycol andmethyl ether may be used as the solvent.

The phosphor which is manufactured by the aqueous solution synthesismethod, the hydrothermal synthesis method, the spray synthesis method,or hydrolysis synthesis method is used as a phosphor in the presentembodiment. Specific method of manufacturing the phosphor of each colorwill be described.

First, a green phosphor will be described. In the case where the M isCa, the synthesis of (Ca_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ will be firstlydescribed.

In the phosphor, when the above-described phosphor composition isexpressed by a chemical formula, it becomes aCaO.xEuO.yTbO.MgO.2SiO₂.Here, it will be described with respect to a case in which a=2.

First, in a step of preparing a mixture, each material of calciumnitrate Ca(NO₃)₂, magnesium nitrate Mg(NO₃)₂, silicon oxide SiO₂(colloidal silica), europium nitrate Eu(NO₃)₃, and terbium nitrateTb(NO₂)₃, which are raw materials of the phosphor, are mixed such that amolar ratio in the chemical formula becomes a:1:2:x:y (a=2, 0.02≦x≦0.2,0≦y≦0.05), and the resultant mixture is dissolved in an aqueous mediumto prepare the mixture (hydrated mixture). As the aqueous medium,ion-changed water or pure water is preferable from a point of view of noincluding impurity. However, even though non-aqueous medium (methanol,ethanol, or the like) is contained thereto, it can be used.

Next, an alkaline solution (for example, potassium hydroxide) is addedto the hydrated mixture to thus prepare a sphere-shaped hydrate (aprecursor of the phosphor). The sphere-shaped hydrate is input to acontainer made of gold or platinum which has corrosion-resistance andheat-resistance and a hydrothermal synthesis reaction is performed usingan device such as an autoclave which is capable of heating whilepressuring. The hydrothermal synthesis reaction is performed in thehighly pressured container under a condition of a predeterminedtemperature (for example, 100° C. to 300° C.) and a predeterminedpressure (for example, 0.2 MPa to 10 MPa), for 12 hours to 20 hoursafter alumina or graphite powder is input to the container as a reducingagent, thereby manufacturing a substantially spherical precursor powderof the phosphor.

Further, the substantially spherical precursor powder of the phosphormay be manufactured by the spray synthesis method of spraying thehydrated mixture into a furnace heated to a temperature of 1,000° C. to1,500° C. directly from the pressured nozzle while applying ultrasonicwaves, instead of using the autoclave.

Next, the precursor powder of the phosphor is baked at a reducingatmosphere (for example, atmosphere containing hydrogen 5% and nitrogen95%) under a condition of a predetermined temperature and apredeterminedtime (for example, at a temperature of 800° C. to 1,400° C., for 2hours). Then, the powder is sorted to thus obtain a desired greenphosphor (Ca_(2-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (Ca₂MgSi₂O₆:Eu, Tb).

Here, the method of obtaining the green phosphor expressed by(Ca_(2-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ in the case in which M=Ca, a=2 wasdescribed. However, to obtain the green phosphor expressed by(Ca_(1-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ in the case in which M=Ca, a=1, theranges of x and y are defined as 0≦x≦0.1, 0.01≦y≦0.2. Further, to obtainthe green phosphor expressed by (Ca_(3-x-y)Eu_(x)Tb_(y))O.MgO,2SiO₂ inthe case in which M=Ca, a=3, the ranges of x and y are defined as0≦x≦0.1, 0.01≦y≦0.2. As described above, it is possible to obtain thegreen phosphor in which a composition ratio of Ca is different bychanging the mixing ratio of the raw materials of the phosphor and usingthe same method.

Further, in the case in which M=Sr, strontium nitrate Sr (NO₃)₂ may beused instead of the Ca(NO₃)₂ as the raw material of the phosphor, and inthe case in which M=Ba, barium nitrate Ba(NO₃)₂ may be used instead ofthe Ca(NO₃)₂ as the raw material of the phosphor

In any case, the phosphor particle obtained by the hydrothermalsynthesis method or the spray synthesis method has a substantiallyspherical shape, and the particle size thereof is smaller than that ofparticle obtained by the conventional solid-phase reaction.

Next, the synthesis method of [(Ca, Sr,Ba]_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ in the case in which M is a mixtureof Ca, Sr, and Ba, will be described.

In the above described phosphor, when a composition thereof is expressedby a chemical formula, it becomes a(Ca, Sr, Ba)O.xEuO.yTbO.MgO.2SiO₂.Here, (Ca, Sr, Ba)O is formed only by substituting a part of Ca with Sror Ba (a ratio of Ca/(Sr, Ba) is 0.1 to 1). Hereinafter, it will bedescribed with respect to the hydrolysis synthesis method in the case inwhich a=2.

As raw materials of the phosphor, calcium alkoxide Ca(O.R)₂, strontiumalkoxide Sr (O.R)₂, barium alkoxide Ba(O.R)₂ (a ratio of Ca/(Sr, Ba) is0.1 to 1.0), magnesium alkoxide Mg (O.R)₂, silicon alkoxide Si(O.R)₄,europium alkoxide Eu(O.R)₃, and terbium alkoxide Tb(O.R)₃ (here, R is analkyl group) are used. The raw materials are mixed such that a molarratio in the chemical formula becomes a:1:2:x:y (a=2, 0.02≦x≦0.2,0≦y≦0.05). Here, the molar ratio a represents a total amount ofCa(O.R)₂, Sr(O.R)₂, and Ba(O.R)₂. Molar ratio after this corresponds tothe describing order of the phospher materials, a molar ratio ofMg(O.R)₂ is 1, a molar ratio of Si(O.R)₄ is 2, a molar ratio of Eu(O.R)₃is x, and a molar ratio of Tb(O.R)₃ is y. Then, water or alcohol isadded to hydrolyze the resultant mixture of the raw materials of thephosphor, which has an alkyl group. The hydrolyzed precursor having asubstantially spherical shape is baked at a temperature of 900° C. to1300° C. Then, it is baked under a reducing atmosphere, for example, anatmosphere of hydrogen 5% and nitrogen 95%, and at a condition ofpredetermind temperature and predetermined time (for example, two hoursat a temperature of 1000° C. to 1400° C.), and is sorted using an airsorter to thus obtain a green phosphor by the hydrolysis synthesismethod.

Further, the values of ‘a’ of Ca, Sr, and Ba can be arbitrary selectedas 1, 2, or 3, and a particular change is not seen at a parent crystalstructure in each case. However, the temperature characteristic of thephosphor, specifically, the characteristic deterioration of the phosphorwith respect to the temperature history during the time of manufacturingPDP becomes small as ‘a’ is large. Further, the baking temperature inthe various synthesis methods described above need to be high when thevalue of ‘a’ is large. Therefore, the value of ‘a’ can be arbitraryselected depending on the process condition of manufacturing thephosphor and the process condition of manufacturing the PDP.

Further, Ca, Sr, and Ba may be used individually or may be used as amixture thereof. In the case in which they are used individually, thecharacteristic deterioration of the phosphor with respect to thetemperature history is in the order of Ba<Sr<Ca. Therefore, thesematerials may be arbitrary selected depending on the process conditionof manufacturing the PDP.

Next, a blue phosphor will be described. A synthesis method ofBa_(1-x)MgAl₁₀O₁₇:Eu_(x) or Ba_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x) as the bluephosphor will be described.

The specific method of manufacturing the blue phosphor is as follows.For example, Ba(NO₃)₂, Sr(NO₃)₂, Mg(NO₃)₂, Al(NO₃)₃, and Eu(NO₃)₃ areused as raw materials of the phosphor. A spherical precursor of thephosphor is manufactured from the aqueous solution of the raw materialsof the phosphor similarly to the synthesis of the green phosphor. Then,in the hydrothermal synthesis process using the precursor, thehydrothermal synthesis reaction is performed at a state in which atemperature is 100° C. to 300° C., and a pressure of 0.2 MPa to 10 MPais applied. The powder obtained from the reaction is heat-treated inH₂—N₂, and sorted to thus obtain the blue phosphor.

Hereinafter, it will be described with respect to a red phosphor. Asynthesis method of (Y, Gd)_(1-x)BO₃:Eu_(x) as the red phosphor will bedescribed.

In a step of preparing a mixture, yttrium hydroxide Y (OH)₃, gadoliniumhydroxide Gd(OH)₃, boric acid H₃BO₃, and europium hydroxide Eu(OH)₃,which are raw materials of the phosphor, are mixed together anddissolved in ion exchange water to have a molar ratio of(Y(OH)₃+Gd(OH)₃):H₃BO₃:Eu(OH)₃=1-x:1:x (0.05≦x≦0.20) (Y:Gd=65:35),thereby preparing a mixture. Next, in the step of preparing a hydrate,an alkaline aqueous solution (for example, ammonia aqueous solution) isadded to the mixture, thereby preparing the hydrate.

Then, in a hydrothermal process, the hydrate and the ion-changed waterare input to a container made of gold or platinum which hascorrosion-resistance and heat-resistance and a hydrothermal synthesisreaction is performed using an device such as an autoclave. Thehydrothermal synthesis reaction is performed in the highly pressuredcontainer under a condition of a predetermined temperature (for example,100° C. to 300° C.), a predetermined pressure (for example, 0.2 MPa to10 MPa), and a predetermined time (for example, 3 to 12 hours). Theobtained phosphor has a particle size of 0.1 μm to 2.0 μm and aspherical shape. The phosphor is heat-treated in the air at atemperature of 800° C. to 1,200° C. for 2 hours and sorted, therebyobtaining a red phosphor.

Hereinafter, a synthesis method of (Y_(1-x))₂O₃:Eu_(x) as a red phosphorwill be described.

In a step of preparing a mixture, yttrium nitrate Y(NO₃)₃ and europiumnitrate Eu(NO₃)₃, which are raw materials of the phosphor, are mixedtogether and dissolved in ion-changed water to have a molar ratio of2(1-x):x (0.05≦x≦0.30). Next, in a step of preparing a hydrate, analkaline aqueous solution (for example, ammonia aqueous solution) isadded to the mixture, thereby preparing the hydrate.

Then, in a hydrothermal process, the hydrate and the ion-changed waterare input to a container made of gold or platinum which hascorrosion-resistance and heat-resistance and a hydrothermal synthesisreaction is performed using an device such as an autoclave. Thehydrothermal synthesis reaction is performed in the highly pressuredcontainer in a temperature of 100° C. to 300° C., at a pressure of 0.2MPa to 10 MPa, and for 3 to 12 hours. The obtained compound is dried tothus obtain a predetermined (Y_(1-x))₂O₃:Eu_(x).

Next, the phosphor is annealed in the air at a temperature of 800° C. to1,200° C. for 2 hours and sorted, thereby obtaining a red phosphor. Thephosphor obtained from the hydrothermal synthesis process has a particlesize of 0.1 μm to 2.0 μm and a spherical shape. Such particle size andshape are suitable for forming a phosphor layer excellent in lightemission characteristic.

The phosphor particle described above is manufactured by thehydrothermal synthesis method, the spray synthesis method, and thehydrolysis synthesis method by using a spherical shaped precursorsynthesized in an aqueous solution. Therefore, the particle has thespherical shape and small particle size, as described above (a meanparticle size is 0.1 μm to 2.0 μm).

As described above, in the phosphor particle manufactured by usingspherical shaped precursor rather than the conventional solid-phasereaction, consolidation due to cohesion during the baking process issuppressed, so that a particle size distribution becomes uniformed.Further, nitrate compound and hydrated compound were used as a startingmaterial. However, for example, metal alkoxide M(O.R)₂, or acetylacetone M(C₅H₇O)₂ (here, M is metal) may be used, in addition to thecompounds described above.

Further, in the above-described red phosphor layer 110R, green phosphorlayer 110G, and blue phosphor layer 100B of PDP 100, the phosphorparticle manufactured by the hydrothermal synthesis method is used tothe whole phosphor layer, but it is also possible to manufacturephosphor layers with same characteristics by the aqueous solutionsynthesis and the spray synthesis method.

In three colors of R, G, and B, especially, the conventional greenphosphor of Zn₂SiO₄:Mn structure had a low brightness compared to otherphosphor, and the deterioration of the brightness was large. Therefore,in the case in which the three colors were simultaneously emitted,color-temperature of white had a tendency to be decreased. Thus, in theplasma display device, the brightness of the discharge cells, in whichphosphor (red and blue) other than green were formed, was lowered usinga circuit to improve color temperature of white display. However, whenusing the green phosphor expressed by M_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂(M is at least one element selected from Ca, Sr, and Ba) manufactured bythe method (method of manufacturing the precursor of the phosphor in theaqueous solution) according to the present invention, the brightness ofthe green discharge cell is high, and it is not necessary to lower thebrightness of the red discharge cell and the blue discharge cell onpurpose. Therefore, it is possible to utilize the brightness of thedischarge cell of each color to the maximum, so that it is possible toincrease the brightness of the plasma display device while thecolor-temperature of the white display being maintained to be high.

Samples were manufactured based on the above-described embodiment and aperformance test experiment was performed for testing the performance ofthe plasma display device according to the invention.

In each manufactured plasma display device, the size thereof was 42inches (HD-TV specification in which the distance (W) between barrierribs 109 was 150 μm), the thickness of dielectric glass layer 105 was 20μm, the thickness of protective layer 160 was 0.5 μm, the distancebetween display electrode 103 and display scan electrode 104, which areformed in a pair, was 80 μm. The discharge gas filled into the inside ofthe discharge spaces was gas composed of Ne (Neon) as a main componentand Xe (Xenon) mixed in an amount of 10%, and filled at a discharge gaspressure of 73 kPa.

The phosphor of each color used in the plasma display device accordingto the embodiment was manufactured by using the precursor in a sphereshape, which was manufactured by the aqueous solution synthesis method,the hydrothermal synthesis method, the spray synthesis method, or thehydrolysis synthesis method. As the green phosphor,M_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (M is at least one element selectedfrom Ca, Sr, and Ba, and a is 1, 2, or 3) was used, as the bluephosphor, Ba_(1-x)MgAl₁₀O₁₇:Eu_(x) or Ba_(1-x-y)Sr_(y)MgAl₁₀O₁₇:Eu_(x)was used, and as the red phosphor, (Y, Gd)_(1-x) BO₃:Eu_(x) or(Y_(1-x))₂O₃:Eu_(x) was used. The phosphor ink used during the time offorming the phosphor layer by using the phosphor of each color wasmanufactured by mixing a phosphor, a resin, a solvent, and a dispersantin a mixing ratio shown in the present embodiment. When the viscosity(25° C.) of the phosphor ink was measured, it was maintained in a rangeof 1,500 CP to 30,000 CP in any phosphor. Further, the formed phosphorlayer was observed, the phosphor ink was uniformly applied to any one ofbarrier ribs on the surface thereof, and the film thickness of thephosphor layer was 20 μm.

Further, in the phosphor of each color used in the plasma display devicein comparative examples, (Y_(0.85))₂O₃:Eu_(0.15) (mean particle size was2 μm) manufactured by the hydrothermal synthesis method was used as thered phosphor, Ba_(0.8)MgAl₁₀O₁₇:Eu_(0.2) (mean particle size was 3 μm)manufactured by the hydrothermal synthesis method was used as the bluephosphor, and Zn₂SiO₄:Mn (mean particle size is 3.2 μm) manufactured bya solid-phase reaction method was used as the green phosphor. Then, thephosphor layer (film thickness was 20 μm) was formed by using thephosphor ink at the same condition as that of the plasma display deviceaccording to the present embodiment.

Experiment to be described later was performed using the described-abovephosphor.

With respect to the samples of the embodiment and the comparativeexample, rate of change in green phosphor brightness was measured duringthe panel sealing process (temperature was 450° C.) in the process ofmanufacturing a panel. Further, rate of change in the brightness duringthe time of performing an accelerated life test of the panel, existenceor nonexistence of address miss during the address discharge, and thebrightness of the panel at the time of turning on the whole surface ofgreen were measured.

The rate of change in the brightness of the green phospher in the panelsealing step was measured as to be described. Specifically, a part of arear glass substrate before sealing the panel after the phosphor layerwas formed was cut out in a predetermined size (for example, about 20mm×10 mm). Then, the sealing of the panel was performed using the rearglass substrate from which a part was cut out, and a part of the rearglass substrate after sealing the panel was cut out in a predeterminedsize (for example, about 20 mm×10 mm). And then, the rear glasssubstrate pieces cut out before and after sealing the panel were set ina vacuum chamber and excimer lamp (vacuum ultraviolet rays was 146 nm)was irradiated thereto, thereby light-emitting the phosphor layer. Thelight emission was measured by using a luminance meter, and the changeof rate (r1) in the brightness was calculated from the brightness ofgreen component before and after sealing the panel by followingequation:r1=(BG1−BG0)/BG0×100

Here, BGO was the brightness of the green component before sealing thepanel, and BG1 was the brightness of the green component after sealingthe panel.

Further, when the brightness of the panel of the plasma display devicewas measured, discharge sustain pulse with a voltage of 150 V and afrequency of 30 kHz was applied to the panel to turn on only the greendischarge cell. The measurement of the rate of change in the brightnessduring accelerated life test of the panel was performed such that adischarge sustain pulse with a voltage of 200V and a frequency of 100kHz was successively applied to the plasma display device for 100 hours,and the brightness of the panel before and after the accelerated lifetest was measured, and the rate of change (r2) in the brightness wasobtained by following equation:r2=(B1−B0)/B0×100

Here, B0 was the brightness before the accelerated life test, and B1 wasthe brightness after the accelerated life test.

Further, in the present experiment, the discharge was uniformlyperformed in color phosphor layers, and the brightness-suppression ofthe discharge cells of red and greens so as to adjust thecolor-temperature at the time of white display was not performed.

Further, to evaluate the address miss during the time of addressdischarge, an image is observed and determined whether a flicker existsor not. Even if one flicker existed, it was expressed by ‘yes’ infollowing tables.

A composition of the phosphor of each color and a mixing condition, inthe case that (M_(1-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (here, M is at leastone element selected from Ca, Sr, and Ba) was used as the greenphosphor, are shown in table 1, and each experiment-measurement resultis shown in table 2. Further, a composition of the phosphor of eachcolor and a mixing condition, in the case that(M_(2-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (here, M is at least one elementselected from Ca, Sr, and Ba) was used as the green phosphor, are shownin table 3, and each experimental measurement result is shown in table4. Further, a composition of the phosphor of each color and a mixingcondition, in the case that (M_(3-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (here, Mis at least one element selected from Ca, Sr, and Ba) was used as thegreen phosphor, are shown in table 5, and each experiment-measurementresult is shown in table 6.

Sample No. 30 in tables 1, 3, and 5 represents comparative example, andsample Nos. 1 to 4 in table 1, sample Nos. 11 to 19 in table 3, andsample Nos. 21 to 25 in table 5 represent the present embodiment. Anitem ‘rate of change (r1) in the brightness’ indicates the rate ofchange (r1) in the brightness of the green phosphor during theabove-described process of sealing the panel, and an item ‘rate ofchange (r2) in the brightness’ indicates the rate of change (r2) in thebrightness during the accelerated life test of the panel. TABLE 1 Greenphosphor (M_(1−x−y)Eu_(x)Tb_(y))O.MgO.2SiO₂ Red phosphor Blue phosphorkind of M and (Y, Gd)_(1−x) BO₃: Eu_(x) Ba_(1−x)MgAl₁₀O₁₇: Eu_(x) Sampleratio of manufacturing manufacturing manufacturing No. x y Ca/Sr/Bamethod X method x method 1 0.01 0.01 M = Ca spray 0.1 hydrolysis 0.05spray synthesis synthesis synthesis method method method 2 0.02 0.1 M =Ca, Ba hydrolysis 0.2 spray 0.1 hydrothermal Ca/Ba = 0.9/0.1 synthesissynthesis synthesis method method method 3 0 0.05 M = Ba, Sr aqueous 0.3Aqueous 0.15 hydrolysis Ba/Sr = 0.1/0.9 solution solution synthesissynthesis synthesis method method method 4 0.1 0.2 M = Ca, Srhydrothermal 0.15 hydrothermal 0.2 hydrolysis Ca/Sr = 0.5/0.5 synthesissynthesis synthesis method method method

TABLE 2 Sam- rate of change rate of change plugging ple in brightness inbrightness address of brightness No. r1 (%) r2 (%) miss nozzle B (cd/m²)1 −1.2 −1.5 no no 305 2 −1.0 −0.5 no no 315 3 −1.3 −0.8 no no 309 4 −1.5−1.2 no no 330 30 −12.7 −14.1 yes yes 275Sample No. 30 is comparative example

TABLE 3 kind of M and Sample ratio of manufacturing manufacturingmanufacturing No. x Y Ca/Sr/Ba method X method x method green phosphorred phosphor blue phosphor (M_(2−x−y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (Y,Gd)_(1−x) BO₃: Eu_(x) Ba_(1−x)MgAl₁₀O₁₇: Eu_(x) 11 0.1 0 M = Ca spray0.1 hydrolysis 0.05 spray synthesis synthesis synthesis method methodmethod 12 0.02 0.01 M = Ca, Ba hydrolysis 0.2 spray 0.1 hydrothermalCa/Ba = 0.9/0.1 synthesis synthesis synthesis method method method 130.05 0.05 M = Ba, Sr aqueous 0.3 aqueous 0.15 hydrolysis Ba/Sr = 0.1/0.9solution solution synthesis method synthesis synthesis method method 140.2 0.01 M = Ca, Sr hydrothermal 0.15 hydrothermal 0.2 hydrolysis Ca/Sr= 0.5/0.5 synthesis synthesis synthesis method method method bluephosphor green phosphor red phosphor Ba_(1−x−y)Sr_(y)MgAl₁₀O₁₇:(M_(2−x−y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (Y_(1−x))₂O₃: Eu_(x) Eu_(x) 15 0.10.02 M = Ca, Ba aqueous 0.01 hydrothermal 0.1 hydrothermal Ca/Ba =0.5/0.5 solution synthesis synthesis synthesis method method method 160.13 0.03 M = Ca, Sr, Ba aqueous 0.1 spray 0.15 spray Ca/Sr/Ba =0.33/0.33/0.33 solution synthesis synthesis synthesis method methodmethod 17 0.05 0.05 M = Sr aqueous 0.15 aqueous 0.2 hydrolysis solutionsolution synthesis synthesis synthesis method method method 18 0.1 0 M =Ca aqueous 0.2 hydrolysis 0.2 hydrolysis solution synthesis synthesissynthesis method method method 19 0.08 0.02 M = Ca, Sr aqueous 0.2hydrolysis 0.2 hydrolysis Ca/Sr = 0.5/0.5 solution synthesis synthesissynthesis method method method

TABLE 4 Sam- rate of change rate of change plugging ple in brightness inbrightness address of brightness No. r1 (%) r2 (%) miss nozzle B (cd/m²)11 −0.8 −1.0 no no 305 12 −1.0 −1.3 no no 315 13 −0.9 −1.2 no no 309 14−0.5 −0.8 no no 330 15 −0.6 −0.9 no no 318 16 −0.5 −0.7 no no 320 17−0.8 −1.0 no no 317 18 −0.7 −0.9 no no 310 19 −0.9 −1.1 no no 320 30−12.7 −14.1 yes yes 275Sample No. 30 is comparative example

TABLE 5 green phosphor blue phosphor (M_(3−x−y)Eu_(x)Tb_(y))O.MgO.2SiO₂red phosphor Ba_(1−x−y)Sr_(y)MgAl₁₀O₁₇: kind of M and (Y_(1−x))₂O₃:Eu_(x) Eu_(x) Sample ratio of manufacturing manufacturing manufacturingNo. x y Ca/Sr/Ba method X method x method 21 0.08 0.1 M = Ca, Ba aqueous0.01 hydrothermal 0.1 hydrothermal Ca/Ba = 0.5/0.5 solution synthesissynthesis method synthesis method method 22 0 0.01 M = Ca, Sr, Baaqueous 0.1 spray 0.15 spray Ca/Sr/Ba = 0.33/0.33/0.33 solutionsynthesis synthesis method synthesis method method 23 0.05 0.2 M = Sraqueous 0.15 aqueous 0.2 hydrolysis solution solution synthesissynthesis synthesis method method method 24 0.1 0.1 M = Ca aqueous 0.2hydrolysis 0.2 hydrolysis solution synthesis synthesis synthesis methodmethod method 25 0.02 0.1 M = Ca, Sr aqueous 0.2 hydrolysis 0.2hydrolysis Ca/Sr = 0.5/0.5 solution synthesis synthesis synthesis methodmethod method

TABLE 6 Sam- rate of change rate of change plugging ple in brightness inbrightness address of brightness No. r1 (%) r2 (%) miss nozzle B (cd/m²)21 −1.2 −0.9 no no 318 22 −1.2 −1.5 no no 320 23 −1.5 −0.8 no no 317 24−1.8 −1.5 no no 310 25 −1.1 −1.1 no no 320 30 −12.7 −14.1 yes yes 275Sample No. 30 is comparative example

As shown in tables 2, 4, and 6, in the comparative sample 10, the rateof change (r1) in brightness during the process of sealing the panel was−12.7%, and the rate of change (r2) in brightness during the acceleratedlife test was −14.1%. Further, the address miss during the addressdischarge existed, and the brightness B of the panel in the case ofgreen-colored whole surface being turned on was 275 cd/m². Further,during the period when ink applying device for applying the phosphor inkwas used for 200 hours, the plugging of the nozzle was generated.

On the other hand, in samples 1 to 4 in the case in which(M_(1-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ was used as the green phosphor, asshown in table 2, the brightness B of the panel in the case ofgreen-colored whole surface being turned on exceeded 300 cd/m² in allsamples. Further, the rate of change (r1) in brightness during theprocess of sealing the panel was from −1.0% to −1.5%, and the rate ofchange (r2) in brightness during ccelerated life test was from −0.5% to−1.5%. Further, the address miss during the address discharge did notexist. Further, during the period when ink applying device for applyingthe phosphor ink was used for 200 hours, the plugging of the nozzle wasnot generated.

Further, in samples 11 to 19 in the case in which(M_(2-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ was used as the green phosphor, asshown in table 4, the brightness B of the panel in the case ofgreen-colored whole surface being turned on exceeded 300 cd/m² in allsamples. Further, the rate of change (r1) in brightness during theprocess of sealing the panel was from −0.5% to −1.0%, andtherateofchange (r2) in brightness during the accelerated life test was from−0.7% to −1.3%. Further, the address miss during the address dischargedid not exist. Further, during the period when ink applying device 200for applying the phosphor ink was used for 200 hours, the plugging ofthe nozzle was not generated.

Further, in samples 21 to 25 in the case in which(M_(3-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂(here, M is at least one elementselected from Ca, Sr, and Ba) was used as the green phosphor, as shownin table 6, the brightness B of the panel in the case of green-coloredwhole surface being turned on exceeded 300 cd/m² in all samples.Further, the rate of change (r1) in brightness during the process ofsealing the panel was from −1.1% to −1.8%, and the rate of change (r2)in brightness during the accelerated life test was from −0.8% to −1.5%.Further, the address miss during the address discharge did not exist.Further, during the period when ink applying device for applying thephosphor ink was used for 200 hours, the plugging of the nozzle was notgenerated.

That is, samples (sample Nos. 1 to 4, 11 to 19, and 21 to 25) accordingto the present embodiment showed excellent characteristics in thebrightness of the panel in the case of green-colored whole surface beingturned on, the rate of change in brightness during the process ofsealing the panel, the rate of change in brightness during theaccelerated life test, the address miss during the address discharge,and the plugging of the nozzle of the ink applying device compared tothe comparative example (Sample No. 30).

That is, the green phosphor according to the invention has a structureof (M_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (here, M is at least one elementselected from Ca, Sr, and Ba) manufactured by the aqueous solutionsynthesis method, the hydrothermal synthesis method, the spray synthesismethod, and the hydrolysis synthesis method, and the relativelysmall-sized phosphor particle (mean particle size is 0.1 μm to 3.0 μm)having a substantially spherical shape is synthesized, so that thegrinding of the particle is not necessary. Further, the deterioration ofthe brightness due to the oxygen defect, which is generated when ZnO isselectively scattered (sublimated) like the conventional Zn₂SiO₄:Mn, isnot generated. Therefore, in the phosphor according to the presentembodiment, the oxygen defect is suppressed, so that the deteriorationof the crystalline property started by the oxygen defect does notreadily proceed. Especially, since the brightness of green issuppressed, and the amount of ultraviolet rays absorbed by the oxygendefect becomes small, the excitation of the light-emission center iseasily performed, thereby the brightness is improved compared to theconventional plasma display device.

INDUSTRIAL APPLICABILITY

According to the plasma display device and the manufacturing methodthereof of the invention, it is possible to provide a plasma displaydevice including a green phosphor of which brightness is hardlydeteriorated, and it is useful to enhance the brightness, the lifetime,and the reliability of the plasma display device as a large-sized imagedisplay device.

1. A plasma display device including a plasma display panel in which aplurality of discharge cells of one color or a plurality of colors aredisposed, a plurality of phosphor layers corresponding to colors of therespective discharge cells are arranged, and the phosphor layers areexcited by ultraviolet rays to emit light, wherein the phosphor layersinclude green phosphor layers, and the green phosphor layers include agreen phosphor expressed by (M_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (here, Mis at least one element selected from Ca, Sr, and Ba).
 2. The plasmadisplay device according to claim 1, wherein, in the green phosphorexpressed by (M_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (here, M is at least oneelement selected from Ca, Sr, and Ba), a=1, 0≦x≦0.1, and 0.01≦y≦0.2. 3.The plasma display device according to claim 1, wherein, in the greenphosphor expressed by (M_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (here, M is atleast one element selected from Ca, Sr, and Ba), a=2, 0.02≦x≦0.2, and0≦y≦0.05.
 4. The plasma display device according to claim 1, wherein, inthe green phosphor expressed by (M_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂(here, M is at least one element selected from Ca, Sr, and Ba), a=3,0≦x≦0.1, and 0.01≦y≦0.2.
 5. The plasma display device according to claim1, wherein, in the green phosphor expressed by(M_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (here, M is at least one elementselected from Ca, Sr, and Ba, the mean particle size of the greenphosphor is 0.1 μm to 3.0 μm, a thickness of the green phosphor layersis 3 μm to 20 μm.
 6. A method of manufacturing a plasma display devicein which a plurality of discharge cells of one color or a plurality ofcolors are disposed, a plurality of phosphor layers corresponding tocolors of the respective discharge cells are disposed, and the phosphorlayers including green phosphor layers are excited by ultraviolet raysto emit light, the method comprising: forming the green phosphor layersincluding a green phosphor expressed by(M_(a-x-y)Eu_(x)Tb_(y))O.MgO.2SiO₂ (here, M is at least one elementselected from Ca, Sr, and Ba), wherein the green phosphor is made by anyone of an aqueous solution synthesis method, a spray synthesis method, ahydrothermal synthesis method, and a hydrolysis synthesis method.
 7. Themethod of manufacturing a plasma display device according to claim 6,wherein a green phosphor synthesis method is comprised of the aqueoussolution synthesis method including the steps of preparing a mixture bymixing a raw material of the phosphor and an aqueous medium, preparing ahydrate by mixing the mixture and an alkaline aqueous solution, andthermally treating a solution containing the hydrate at a temperature of700° C. to 900° C. in the air.
 8. The method of manufacturing a plasmadisplay device according to claim 6, wherein a green phosphor synthesismethod is comprised of the hydrothermal synthesis method comprising thesteps of preparing a mixture by mixing a raw material of the phosphorand an aqueous medium, preparing a hydrate by mixing the mixture and analkaline aqueous solution, and hydrothermally synthesizing a solutioncontaining the hydrate at a temperature of 100° C. to 300° C. and at astate in which a pressure is 0.2 MPa to 10 MPa.
 9. The method ofmanufacturing a plasma display device according to claim 6, wherein agreen phosphor synthesis method is comprised of the spray synthesismethod comprising the steps of preparing a mixture by mixing a rawmaterial of the phosphor and an aqueous medium, preparing a hydrate bymixing the mixture and an alkaline aqueous solution, and spraying thesolution containing the hydrate into a furnace heated to a temperatureof 1000° C. to 1500° C.